4-Hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acids and esters

ABSTRACT

Anti-allergic 4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acids and esters are prepared by reacting a 3,4-dihydro-1,3-dioxo-1H-pyrido[2,3-d][1,3]oxazine (a 3-azaisatoic anhydride) with an alkali metal salt of a malonic ester.

The invention relates to chemical compounds which are4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acids and esters,their preparation, to their use as pharmacological agents, particularlyas anti-allergic agents, and to compositions for such use.

The compounds of the present invention may be represented by thefollowing structural formula I: ##STR1## wherein R° is hydrogen, alkylof 1 to 6 carbon atoms, alkenyl of 3 to 6 carbon atoms, alkynyl of 3 to6 carbon atoms, cycloalkyl of 3 to 6 carbon atoms, cycloalkylalkyl inwhich the cycloalkyl is of 3 to 6 carbon atoms and the alkyl portion isof 1 or 2 carbon atoms, or ##STR2## R" is hydrogen, alkyl of 1 to 4carbon atoms, alkenyl of 3 to 6 carbon atoms or alkynyl of 3 to 6 carbonatoms,

N is 0 or 1,

Y and Y' are independently hydrogen, halo of atomic weight of from 18 to80, i.e., fluoro, chloro or bromo, alkyl of 1 to 3 carbon atoms, alkoxyof 1 to 3 carbon atoms or trifluoromethyl, and

R and R' are independently hydrogen or alkyl of 1 to 4 carbon atoms,with the proviso that the unsaturation in any alkenyl or alkynyl is onother than the alpha carbon atom, or a mono- or di-salt form thereof inwhich the salt forming cation is a pharmaceutically acceptable cation.

The compounds of the formula I in which R" is a hydrocarbon (i.e. alkyl,alkenyl or alkynyl) may be prepared by reacting a compound of theformula II: ##STR3## wherein R°, R and R' are as defined, with acompound of the formula III: ##STR4## in which R_(a) " is alkyl of 1 to4 carbon atoms, alkenyl of 3 to 6 carbon atoms or alkynyl of 3 to 6carbon atoms, and

M is an alkali metal.

The preparation of compounds I in which R" is alkyl, alkenyl or alkynyl(R_(a) ") as above indicated is suitably carried out in an inert organicsolvent, e.g., dimethylacetamide, and at a temperature of from 0° C. to150° C., preferably 60° C. to 130° C., followed, if necessary ordesired, by neutral or acid hydrolysis to obtain the desired compound Ifrom any 4-alkali metal salt thereof initially produced.

The compounds of the formula III may be produced from the correspondingdialkyl, dialkenyl or dialkynyl malonates (IIIA) (which are known typecommands) by reaction with a strong alkali base, e.g., sodium hydride,in an inert organic solvent, e.g., dimethylacetamide.

The compounds of the invention in which R" is R_(a) " and in which theacidic 4-hydroxy group is neutralized to provide such compounds in amonosalt form are also and preferably prepared from a free acid form ofa compound of the formula I in which R" is R_(a) " by procedures wellknown in the art, e.g., by treating with a base such as dilute sodiumhydroxide in a water miscible solvent.

The compounds of the formula I in which R" is hydrogen (and otherwise infree acid form) may be prepared by subjecting a corresponding compound Iin which R" is a highly labile hydrocarbon group, desirably t-butyl, infree acid or 4-monosalt form, preferably in free acid form, to mildtemperature but otherwise conventional acid catalysed decomposition. Insuch reaction the temperature conditions are controlled, e.g., fromminus 20° C. to 60° C., preferably from minus 10° C. to 35° C., in orderto avoid decarboxylation of the compounds I. Acids of known conventionaltypes for such acid decompositions may be employed. Representative suchacids include sulfuric acid, hydrochloric acid and perchloric acid,preferably the latter. The decomposition is suitably carried out inconventional solvent systems for such decompositions, such as a watermiscible non-hydroxylic organic solvent such as acetonitrile,tetrahydrofuran and the like, preferably acetonitrile, such solventsystem preferably containing only small amounts of water.

The compounds of the formula I in disalt form may be prepared bytreating a compound of the formula I in which R" is R_(a) ", eg. ethyl,with a saponifying base, eg. sodium hydroxide, in an aqueous medium, eg.water or aqueous ethanol, at moderate temperatures of from 40° C. to150° C., preferably 80° C. to 120° C., followed by recovery in aconventional manner that avoids acidification that can lead to undesireddecarboxylation. When the starting compound I is in free acid form itwill be evident that at least 2 mols of base are used and in general 2or more mols are preferably employed. Hence, it will be evident thatthis reaction will also affect the 4-position substituent and introducethe cation of the base at the 4-position when the starting compound isin free acid form or produce other compounds I in disalt form in whichthe two salt forming cations may be the same or different when thestarting compound itself is in 4-monosalt form, depending largely onknown factors such as the base and the amount thereof that is used. Awide variety of bases may be employed as will be evident, includingalkali metal hydroxide, alkaline earth metal hydroxides and ammonium andtetraalkylammonium hydroxides. However, the base is preferably an alkalimetal hydroxide and the starting compound in free acid form such thatthe two cations in the disalt form product are the same alkali metal,preferably sodium or potassium.

The compounds of the formula I in free acid form may also be treatedwith 1 mol of essentially any desired base, preferably an alkali metalhydroxide such as sodium hydroxide or potassium hydroxide, in anappropriate solvent such as water or aqueous ethanol and over a widetemperature range up to at least about 150° C., preferably 0° C. to 60°C., to obtain the compounds of the invention in a monosalt form inwhich, because of the tautomerism between the adjacent acidic (4-hydroxyand 3-carboxyl) functions, the salt forming cation is ionicallyassociated with both said 3- and 4-position functions in the knownmanner of essentially forming an additional six membered ring with thecation.

The compound of the formulae II and IIIA are both either known per se ormay be prepared from known materials by procedures known in the art.

In general, the preferred compounds of the formula I have one or moreand preferably all of the following features: a) R° being alkyl oralkenyl, more preferably alkenyl, most preferably allyl; b) R is alkyl(particularly methyl or ethyl) and R' is hydrogen or alkyl (particularlymethyl), more preferably R is 7-methyl or 7-ethyl, most preferably7-methyl and R' is hydrogen; c) R" is hydrogen, alkyl or alkenyl, morepreferably hydrogen or alkyl, most preferably alkyl; and d) thecompounds being in free acid form.

The compounds of formula I, (in ester, free acid or mono- or disaltform) are useful because they possess disodium chromoglycate (DSCG)-likeactivity, in particular histamine release inhibiting activity, and aretherefore useful in the treatment of allergic conditions, such asallergic asthma, as indicated in the passive cutaneous anaphylaxis testin the rat. Female rats (180-200 g) are sensitised by subcutaneousadministration of 1 mg of egg albumin (Merck Nr. 967) and 200 mg.Al(OH)₃ in 1 ml. of physiological saline and 0.5 ml. ofHaemophiluspertussis vaccine (Schweizerisches Serum and Impfinstitut,Bern; Nr. 115 325; 4 × 10¹⁰ organism/ml) intraperitoneally. Fourteendays later, the animals are exsanguinated, the blood centrifuged, theserum collected and deep frozen. The serum thus obtained (anti-serum) isinjected intradermally (0.1 ml of a 1:200 diluted serum per injectionsite) at four sites on the backs of untreated, female rats. Twenty-fourhours later each rat is administered 0.1 to 5.6 mg/kg i.v. or 0.1 to 100mg/kg p.o. of the test compound, and either immediately or 5 to 30minutes afterwards, in the case of intravenous administration, or 15 or60 minutes afterwards, in the case of oral administration, afterwardsegg albumin (5mg/ml i.v.) dissolved in physiological saline containing0.25% Evans Blue dye (Merck Nr. 3169). The egg albumin elicits acutaneous anaphylactic reaction, the intensity of which is proportionalto the extent to which the Evans Blue dye diffuses into the tissuesurrounding each of the four sensitisation sites. Thirty minutes afterthe administration of the egg albumin, the rats are killed with ether,the underside of the skin of the back of each animal is exposed and thediameter of the area of blue dye surrounding each of the foursensitisation sites are measured. Each dose of test compound isinvestigated in between four and six rats and the mean diameter comparedwith the mean value obtained in four solvent-treated control rats. Thepercentage inhibition is taken as the percentage of the mean diameter inthe test animals relative to the mean diameter in the controls.

The DSCG-like activity, in particular histamine release inhibitingactivity, can be confirmed by inhibition of histamine release in the ratperitoneal mast cell test, basically as described by Kusner et al., J.Pharmacol. Exp. Therap. 184, 41-46 (1973), with the followingmodification: after sedimentation of the mast cells by centrifugation at350 × g and 4° C., the sediments are taken up in 1 ml of Hank's balancedsalt solution (HBSS) (buffered to a pH of 6.9) and pooled. The resultingsuspension is centrifuged, washed again with HBSS and sedimented. Thethus purified mast cells are prepared as 2 ml suspensions in HBSS. Tothese are added either 2 ml of HBSS, to determine the spontaneoushistamine release, or 2 ml of HBSS and 2.24 ug of compound 48/80(N-methylhomoanisylamineformaldehyde condesate; a histamine liberatorfrom Burroughs Wellcome and Co. Inc., Tuckahoe, N.Y. USA), to determinethe 48/80 induced histamine release, or 2 ml of HBSS with 2.24 ug of48/80 and from 18 to 180 ug/ml of the test compound, to determine the48/80 induced histamine release in the presence of the test compound.

The 48/80 induced histamine release minus the spontaneous histaminerelease is taken as 100% histamine release. The 48/80 induced histaminerelease in the presence of the test compound minus the spontaneoushistamine release is then compared with the 100% value to determine thepercentage inhibition by the test compound. [The histamine determinationis effected in conventional manner, for example as described in theabove-mentioned Kusner et al. article, or in Kusner and Herzig, Advancesin Automated Analysis, 429 (1971)].

For the above-mentioned use, the dosage administered will, of course,vary depending on the compound employed, mode of administration andtreatment desired at a daily dosage of from about 0.3 to 100 mg/kg inanimal body weight, conveniently given in divided doses two to fourtimes daily, or in sustained release form. For the larger mammals, thetotal daily dosage is in the range of from about 20 to 400 mg of thecompound admixed with a solid or liquid pharmaceutical carrier ofconventional type, and divided dosage forms comprise 5 to 200 milligramsof the compound in admixture with a solid or liquid pharmaceuticalcarrier. As will be appreciated by those skilled in the art, thetreatment of allergic conditions according to the invention is based onhistamine release inhibition activity and is therefore essentiallysymptomatic. The ability to employ such compounds in the prophylactictreatment of such allergic conditions (as evident from the DSCG-likeactivity) is a desirable feature. However, the good oral activityrelative to DSCG is a further feature.

Pharmaceutical compositions provided by the invention and useful fortreating allergic conditions due to histamine release contain a compoundof the formula I (in ester, or in free acid or salt form) as activeingredient and one or more conventional pharmaceutically acceptablecarriers, and such other conventional adjuvants as may be desired ornecessary. Such compositions may be in conventional orallyadministerable forms such as tablets, capsules, granules, dispersiblepowders, elixirs, syrups, suspensions and the like or in conventionalparenterally administerable forms such as an injectable sterilesolution, suspension or the like, e.g., a sterile injectable aqueoussuspension. Such compositions including applicable unit dosage formsthereof may be prepared according to any method known in the art for themanufacture of pharmaceutical compositions. The compounds may also beadministered by inhalation therapy techniques in compositionsconventionally prepared and adapted for such procedures. In general, thecompositions of the invention adapted for either oral, inhalation orparenteral administration may conatin from 1% to 90% by total weight ofactive ingredient in combination with the carrier, more usually 3% to70%. The preferred unit dosage forms are the essentially solid formsadapted for oral administration, e.g., tablets or capsules.

A representative formulation for administration 2 to 4 times a day forprophylatic treatment of allergic asthma is a capsule prepared bystandard techniques to contain the following:

    ______________________________________                                        Ingredients             Weight (mg.)                                          ______________________________________                                        1-allyl-7-methyl-4-hydroxy-pyrido                                             [2,3-b]pyridine-2(1H)-one-3-carboxylic                                        acid ethyl ester        40                                                    Kaolin                  210                                                   ______________________________________                                    

The following examples are given for purposes of illustration only.

EXAMPLE 11-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]-pyridine-2(1H)-one-3-carboxylicacid ethyl ester. ##STR5##

To a solution of 3.0 g. of diethyl malonate in 50 ml. ofdimethylacetamide is added portionwise 0.9 g. of pentane washed 50%sodium hydride whereby hydrogen gas is released. The resulting solutionis stirred at room temperature for 20 minutes. There is then added asolution of 4.0 g. of4,6-dimethyl-3,4-dihydro-1,3-dioxo-1H-pyrido[2,3-d][1,3]oxazine in 50ml. of dimethylacetamide. The resulting mixture is stirred at 120° C.for 4 hours. The dimethylacetamide is removed in vacuo, water added, themixture washed with methylene chloride, acidified with 2N. hydrochloricacid and extracted into methylene chloride. The organic phase is driedand evaporated to an oil which is crystallized from methylenechloride/ether/pentane to obtain1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester, m.p. 122°-125° C.

EXAMPLE 2

Following the procedure of Example 1, the following compounds of theinvention are prepared.

(A)1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine2(1H)-one-3-carboxylicacid allyl ester.

(B)1-propargyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.

(C)1-cyclopropylmethyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.

(D) 1-phenyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acidethyl ester.

(E)1-benzyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.

(F) 1-(p-fluorobenzyl)-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acid ethyl ester.

(G) 1,7-dimethyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester, m.p. 148°-151° C.

(h) 7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acidethyl ester.

(I)1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine2(1H)-one-3-carboxylicacid t-butyl ester.

(J)1,6,7-trimethyl-4-hydroxy-pyrido[2,3-b]pyridine2(1H)-one-3-carboxylicacid ethyl ester.

(K)1-allyl-6,7-dimethyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.

(L)1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine2(1H)-one-3-carboxylicacid n-butyl ester.

EXAMPLE 3

A solution of 2.0 grams of1-allyl-7-methyl-4-hydroxypyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid t-butyl ester in 25 ml. of acetonitrile is treated with 0.7 ml. of60% aqueous perchloric acid at 0° C. The resulting precipitate isfiltered off and washed with ether to obtain1-allyl-7-methyl-4-hydroxypyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid.

What is claimed is:
 1. A compound having in free acid form the formula:##STR6## wherein R° is hydrogen, alkyl of 1 to 6 carbon atoms, alkenylof 3 to 6 carbon atoms, alkynyl of 3 to 6 carbon atoms, cycloalkyl of 3to 6 carbon atoms, cycloalkylalkyl in which the cycloalkyl is of 3 to 6carbon atoms and the alkyl portion is of 1 or 2 carbon atoms, or##STR7## R" is hydrogen, alkyl of 1 to 4 carbon atoms, alkenyl of 3 to 6carbon atoms or alkynyl of 3 to 6 carbon atoms,n is 0 or 1, Y and Y' areindependently hydrogen, fluoro, chloro, bromo, alkyl of 1 to 3 carbonatoms, alkoxy of 1 to 3 carbon atoms or trifluoromethyl, and R and R'are independently hydrogen or alkyl of 1 to 4 carbon atoms, with theproviso that the unsaturation in any alkenyl or alkynyl is other than onthe alpha carbon atom; or a mono- or di-salt form thereof in which thesalt forming cation is a pharmaceutically acceptable cation.
 2. Acompound of claim 1 in which R" is hydrogen, alkyl or alkenyl.
 3. Acompound of claim 1 in which R° is alkyl.
 4. A compound of claim 1 inwhich R° is alkenyl.
 5. A compound of claim 1 in which R° is alkynyl. 6.A compound of claim 1 in which R° is cycloalkyl.
 7. A compound of claim1 in which R° is cycloalkylalkyl.
 8. A compound of claim 1 in which R°is ##STR8##
 9. A compound of claim 8 in which n is
 0. 10. A compound ofclaim 8 in which n is
 1. 11. A compound of claim 1 in a free acid form.12. A compound of claim 4 in which R° is allyl.
 13. A compound of claim3 in which R° is methyl.
 14. The compound of claim 1 in which R is alkyland R' is hydrogen or alkyl.
 15. The compound of claim 1 in which R is7-methyl and R' is hydrogen.
 16. A compound of claim 11 in which R" ishydrogen.
 17. A compound of claim 2 in which R" is alkyl.
 18. A compoundof claim 3 in which R is methyl and R' is hydrogen or methyl.
 19. Acompound of claim 4 in which R is methyl and R' is hydrogen or methyl.20. A compound of claim 14 in which R is methyl and R' is hydrogen. 21.A compound of claim 18 in which R is 7-methyl.
 22. A compound of claim19 in which R is 7-methyl.
 23. The compound of claim 22 which is1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.
 24. The compound of claim 21 which is1,7-dimethyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acidethyl ester.
 25. The compound of claim 22 which is1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid t-butyl ester.
 26. The compound of claim 22 which is1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-carboxylicacid.
 27. The compound of claim 22 which is1-allyl-6,7-dimethyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.
 28. The method of symptomatically treating allergicconditions due to histamine release comprising administering to a mammalin need of such treatment an allergy treating effective amount of acompound of claim
 1. 29. The method of claim 28 in which the compound isa compound in which R° is alkyl or allyl.
 30. The method of claim 29 inwhich R° is methyl or allyl.
 31. The method of claim 29 in which R ismethyl and R' is hydrogen or methyl.
 32. The method of claim 31 in whichR is methyl and R' is hydrogen.
 33. The method of claim 32 in which R is7-methyl.
 34. The method of claim 33 in which the compound is1,7-dimethyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylic acidethyl ester.
 35. The method of claim 33 in which the compound is1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid ethyl ester.
 36. The method of claim 33 in which the compound is1-allyl-7-methyl-4-hydroxy-pyrido[2,3-b]pyridine-2(1H)-one-3-carboxylicacid.
 37. A pharmaceutical composition comprising an inertpharmaceutically acceptable carrier and an amount of a compound of claim1 effective to symptomatically treat allergic conditions.